1. Field of the Invention
This invention relates to an objective lens and a scanning microscope provided with the objective lens.
2. Description of Related Art
One of conventional scanning microscopes is constructed so that light from a light source is transmitted by an optical fiber and the top face of the optical fiber is moved together with a lens (refer to Japanese Patent Kokai No. 2002-40359).
In an optical system disclosed in Kokai No. 2002-40359, monochromatic aberrations are favorably corrected. However, chromatic aberration is not completely corrected.
It is, therefore, an object of the present invention to provide an objective lens in which chromatic aberration is completely corrected and a scanning microscope provided with this objective lens.
In order to achieve the above object, the objective lens according to the present invention includes a first lens unit with positive refracting power and a second lens unit placed on the specimen side of the first lens unit. The first lens unit has at least one lens and the second lens unit has at least one optical element, satisfying the following conditions:       v    dLD     greater than             v      dHD        ⁢          
        -    0.56    ≦            φ              II        ⁢              /          φ      T        ≦  0.56
where xcexddLD is the Abbe""s number of glass material of the lens, xcexddHD is the Abbe""s number of glass material of the optical element, xcfx86II{circle around (1)} is the refracting power of a first surface of the second lens-unit, and xcfx86T is the refracting power of the entire system of the objective lens.
The objective lens also satisfies the following conditions:
xcexddHDxe2x89xa626
dIIxcfx86Txe2x89xa70.63
where dII is a face-to-face spacing of the optical element of the second lens unit.
The scanning microscope according to the present invention includes a probe section having the objective lens, an actuator, and an optical fiber and a body section having a point source, a photodetector, and a light-splitting element.
This and other objects as well as the features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.